Perishable, temperature-sensitive materials and goods must be stored and preserved at optimal storage temperatures. Depending upon the type of perishable materials or goods being preserved, the optimal storage temperature required inside the storage container may be relatively high or low compared to the ambient temperature outside the container. In many instances, the materials or goods must be preserved or stored inside the container for several days during which time the optimal storage temperature must be maintained.
Conventional insulating containers use foam or other types of insulating materials placed between the outer walls of the container and the inside insulated space. The amount of heat that is transferred through these materials is proportional to the material's thermal conductivity, the length of time for exposure, the thickness of the material, and the temperature gradient between the material's inside and outer surface. Since these materials have relatively moderate thermal conductivity properties, the thickness of the material must be increased in order to reduce the amount of heat transfer. In the shipping industry, for example, where shipping space is often limited, the use of thick, bulky insulating material is usually undesirable.
Therefore, insulating panels or shapes that can efficiently maintain optimal storage temperatures for extended time periods and which are compact and occupy minimal space are highly desireable. In addition, insulating panels or shapes which can be used either separately or placed inside a rigid, conventional container are also highly desirable.
In the insulation field, it is known that a container having a vacuum space between its outer and inner surface, can act as an excellent insulator. In order to support the enclosed vacuum space, however, the container must have a strong rigid structure to support the large pressure loads that exist on the container's outer and inner surfaces. In the past, cylindrical-shaped containers having an internal vacuum insulating space have been used for preserving liquid materials and other goods. These containers, typically, have relatively large, outer rigid structures.
McAllister, (U.S. Pat. No. 4,446,934) discloses a large, self-containing, vacuum insulating shipping container having inner and outer wall sections with membranes enclosing two structural support frames. The membranes of the outer wall section curve inwardly and the membranes of the inner wall section curve outwardly with the pressure loads imparted on each set of membranes being transmitted into their respective structural support frame. The structural support frames are separated by supports.
Anderson, (U.S. Pat. No. 3,370,740) discloses a double wall, thermal insulating evacuated panel having an internal support structure which resists collapse of the walls caused by external ambient forces. The support structure comprises a series of post-like supports extending perpendicular from the inner surface of the walls with tension cables extending over the ends of the supports.
Dinsmore, et al., (U.S. Pat. No. 2,633,264,) discloses a double wall thermos unit having an outer and an inner shell with an evacuated space created between the shells with no apparent internal support structure. The evacuated space may contain dead air space or be evacuated or filled with insulating material.
Schultz, (U.S. Pat. No. 1,337, 278) discloses a vacuum container having generally a cylindrical shape with outer and inner walls formed of wood or some other rigid material, a vacuum space located between the walls, and supporting strips.
None of these patents disclose a vacuum insulating panel or shape that has the features or methods disclosed herein.